U.S. patent number 5,393,296 [Application Number 07/987,654] was granted by the patent office on 1995-02-28 for method for the medical treatment of pathologic bone.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Manfred Rattner.
United States Patent |
5,393,296 |
Rattner |
February 28, 1995 |
Method for the medical treatment of pathologic bone
Abstract
The invention relates to a method for stimulating bone growth in
a mammal. The method comprises the step of exposing a bone zone
where bone growth is to occur to cavitation for bringing forth
haemorrhage and/or microfissures and/or to at least partially
loosened bone chips at said bone zone.
Inventors: |
Rattner; Manfred
(Grossenseebach, DE) |
Assignee: |
Siemens Aktiengesellschaft
(Munich, DE)
|
Family
ID: |
25533442 |
Appl.
No.: |
07/987,654 |
Filed: |
December 9, 1992 |
Current U.S.
Class: |
601/2;
607/51 |
Current CPC
Class: |
A61N
7/00 (20130101) |
Current International
Class: |
A61N
7/00 (20060101); A61B 017/56 () |
Field of
Search: |
;128/24AA,660.03,24EL
;607/51,50 ;601/2,3,4 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pfaffle; Krista M.
Attorney, Agent or Firm: Hill, Steadman & Simpson
Claims
What I claim is:
1. A method for stimulating bone growth in a mammal comprising the
step of applying acoustic rarefaction pulses to a bone zone where
bone growth is to occur, said step of applying generating at said
bone zone and producing at least one symptom of the group
consisting of haemorrhage, microfissures and at least partially
loosened bone chips at the bone zone.
2. The method of claim 1, further comprising the step of focussing
said rarefaction pulses on the bone zone.
3. A method for stimulating bone growth in a mammal comprising the
step of applying a series of positive acoustic pressure pulses each
followed by a decrease of pressure to a bone zone where bone growth
is to occur, said step of applying generating at said bone zone and
producing at least one symptom group consisting of haemorrhage,
microfissures and at least partially loosened bone chips, said
series of positive acoustic pressure pulses having a repetition
frequency for superimposing cavitational effects at said bone zone
due to the decrease of pressure of a plurality of successive ones
of said pressure pulses.
4. The method of claim 3, wherein said repetition frequency is at
least 3 Hz.
5. The method of claim 3, further comprising the step of focussing
said series of pressure pulses on the bone zone.
6. The method of claim 3 wherein said repetition frequency is at
least 10 Hz.
7. A method for stimulating bone growth in a mammal comprising the
step of applying ultrasound waves having both positive and negative
half cycles to a bone zone where bone growth is to occur, said step
of applying generating cavitation at said bone zone and producing
at least one symptom of the group consisting of haemorrhage,
microfissures and at least partially loosened bone chips.
8. The method of claim 7, wherein the step of applying said
ultrasound waves is further defined by applying said ultrasound
waves in the form of ultrasound bursts, each burst comprising at
least one cycle of said ultrasound wave.
Description
FIELD OF THE INVENTION
The invention relates to the medical treatment of bone pathology,
e.g. delayed fracture healing, pseudoarthrosis etc., by applying
acoustic energy to the site to be treated. More specifically the
invention relates to a method for stimulating bone growth in a
mammal by applying acoustic energy to a region of the bone where
bone growth is to occur.
1. Description of the Prior Art
In a known method of this kind focussed shock waves are applied to
the site to be treated. The intensity of the shock waves is such
that haemorrhage occurs at the site to be treated (see U.S. Pat.
No. 4,905,671). This method requires a high amount of acoustic
energy to be applied to the patient.
2. Objects of the Invention
It is an object of the invention to develop a method for the
medical treatment of bone pathology which allows for inducing bone
growth at the site to be treated at low energy amounts. This and
other objects of the invention will become evident from the
following description of the invention.
SUMMARY OF THE INVENTION
The above object is achieved in a method for stimulation bone
growth in a mammal comprising the step of exposing a bone zone
where bone growth is to occur to cavitation for bringing forth at
the bone zone to be treated at least one symptom of the group
consisting of haemorrhage, microfissures and at least partially
loosened bone chips. Due to cavitation in the tissue surrounding
the bone zone to be treated, disruptive effects are exerted on the
tiny blood vessels of the periosteum and the cortical bone below
the periosteum. Cavitation in this region occurs at modest energy
doses applied to the patient, so haemorrhage and/or microfissures
and/or at least partially loosened bone chips can be induced at low
energy amounts applied to the mammal. As is known from U.S. Pat.
No. 4,905,671 haemorrhage at the treated bone zone leads to the
formation of a so called fraction haematoma which is supposed to be
the seed for bone growth. Inducing microfissures and/or at least
partially loosening bone chips is also favourable for bringing
forth bone growth.
Cavitation is preferably induced by applying acoustic energy to the
bone zone to be treated. This can be, for instance, effected by
applying acoustic rarefaction pulses to the bone zone to be
treated, the rarefaction pulses having an intensity, i.e. an energy
content, sufficient to bring forth at least one symptom of the
above cited group of symptoms.
If rarefaction pulses are applied, it can be most useful to focus
the rarefaction pulses. In this way cavitation is limited to the
very site where treatment is to occur. Besides, by focussing the
rarefaction pulses cavitation can be induced at even lower energy
doses applied to the patient.
Cavitation at the bone zone to be treated can also be brought forth
by applying a series of (positive) acoustic pressure pulses, e.g,
shock waves, with a repetition frequency high enough to prevent the
tissue surrounding the bone zone to be treated from recovering from
the effect of the decrease of pressure following each pressure
pulse. Cavitation is brought forth in this way by superposition of
the cavitational effects due to the decrease of pressure of a
plurality of successive pressure pulses.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention reference should be
made to the accompanying drawings in which there is illustrated and
explained a preferred embodiment of the invention.
FIG. 1 shows an acoustic pulse generator for generating acoustic
rarefaction pulses, applied to an arm with a fractured upper arm
bone;
FIG. 2 shows the sites of the fracture of the upper arm bone at
which rarefaction pulses are to be applied.
DETAILED DESCRIPTION
FIG. 1 shows an acoustic pulse generator for generating acoustic
rarefaction pulses of the type described in detail in co-pending
U.S. patent application Ser. No. 07/739,179, now U.S. Pat. No.
5,309,897, the disclosure of which is herewith incorporated by
reference.
The generator serves the purpose of irradiating pathologic bone
zones, for instance fractures, pseudoarthrosis etc., by exposing
the pathologic bone zone to cavitation. In FIG. 1 an upper arm 1 is
illustrated with an upper arm bone B having suffered a fracture
2.
The generator has central acoustic pulse source 3 which generates
positive acoustic pressure pulses. These propagate radially
outwardly in an liquid acoustic propagation medium contained in a
housing 4 closed at its application end by a flexible application
bellows 5.
The acoustic pulse source 3 is surrounded by a reflector 6 arranged
inside housing 4 and having a reflecting surface 7 of parabolic
shape. As the acoustic pulses emanating from the acoustic pulse
source 3 are cylindrical wave pulses and as the acoustic pulse
source 3 and the reflecting surface 7 have the same central axis,
an acoustic pulse generated by the acoustic pulse source 3 is
focussed by the reflector 6 to a focus zone outside bellows 5. The
center of the focus zone is referenced F.
The reflector 6 is an acoustically soft reflector, i.e. the
reflection of incident acoustic pulses occurs at a boundary surface
to a medium which is acoustically soft compared to the acoustic
propagation medium. The acoustic impedance of the medium having the
boundary surface, thus is lower than that of the propagation
medium. Reflector 6 therefore has a negative reflection factor.
This means a positive acoustic pressure pulse emanating from pulse
source 3 is refleced at the reflecting surface 7 as an acoustic
rarefaction pulse, i.e. a negative pressure pulse, which is
converged to the focus zone.
The generator is applied by means of application bellows 5 to upper
arm 1 in a position such that the center F of the focus zone lies
at the edge of fracture 2 on the left side of fracture 2. This
achieved with the aid of an ultrasound locating system, known per
se, the ultrasound applicator 8 of which is received in a central
bore of the pulse source 3.
The generator and the upper arm 1 are displaced relative to each
other for treatment of fracture 2 such that the focus zone of the
rarefaction pulses is moved point by point along the edge of
fracture 2 on each side of fracture 2. At each point of the
movement at least one rarefaction pulse, preferably a series of
rarefaction pulses, is applied to the edge of fracture 2. In FIG. 2
the points of the movement, i.e. the sites of rarefaction pulse
application, are referenced R1 to R8 on the right and L1 to L8 on
the left side of the fracture 2, respectively. If the upper arm
bone B is aligned properly and the focus zone is sufficiently
large, rarefaction pulses can be applied to corresponding sites on
the left and right side of the fracture, e.g. sites L1 and R1,
jointly.
The intensity of the rare faction pulses is such, that due to
cavitation broght forth by these pulses, haemorrhage at the site of
rarefaction pulse application occurs due to rupture of the small
blood vessels of the periosteum and/or microfissures are induced
and/or bone chips are at least partially loosend in the region of
cortical bone situated below the periosteum. This results in the
formation of a fracture haematoma which as well as microfissures
and at least partially loosened bone chips is known to inducce bone
growth even in the case of delayed bone consolidation.
Preferred peak pressure amplitude of the rarefaction pulses is
about 100 bar (negative) though higher and even lower peak pressure
amplitudes are possible.
The movement between generator and upper arm preferably is effected
in a fashion such that points of rarefaction pulse application are
separated from each other by a distance not greater than the
respective dimension of that region of the focus zone within which
the intensity of the rarefaction pulses is sufficient to induce
haemorrhage and/or microfissures and/or to at least partially
loosen bone chips.
Cavitation at the bone zone to be treated can also be brought forth
by applying to the site to be treated a series of (positive)
acoustic pressure pulses, e.g. shock waves, with a repetition
frequency high enough to prevent the tissue surrounding the bone
zone to be treated from recovering from the effect of the decrease
of pressure following each pressure pulse. Cavitation is brought
forth in this way by superposition of the cavitational effects due
to the decrease of pressure of a plurality of successive pressure
pulses.
The pressure pulses are preferably focussed for the same reasons as
in the case of the rarefaction pulses. The repetition frequency is
at least 3 Hz, preferably at least 10 Hz.
The generator for generating the pressure pulses can be constructed
just the same as the generator for generating the rarefaction
pulses described above, with the sole exemption that an
acoustically hard reflector is used. A pressure pulse generator of
this type is described in U.S. Pat. No. 5,058,569, the disclosure
of which is herewith incorporated by reference. Also incorporated
by reference are the disclosures of U.S. Pat. Nos. 4,674,505 and
4,928,672, in which a further type of generator for generating
acoustic pressure pulses is described.
Acoustic rarefaction pulses can also be generated, for instance, by
applying an electric current pulse of suitable polarity to a
piezoelectric pressure pulse generator of the type disclosed in
U.S. Pat. No. 4,526,168, the disclosure of which is herewith
incorporated by reference.
Cavitation can also be induced by exciting an ultrasound wave
source to periodical oscillation for generating ultrasound waves
having both positive and negative half cycles and applying the
generated ultrasound waves to the site to be treated. Cavitation
will then occur during the negative half cycles.
To prevent the bone and the surrounding tissue at the site to be
treated from becomming heated by the ultrasound waves to
physiologically unsuitable temperatures the ultrasound waves may be
generated in the form of so called ultrasound bursts, with each
burst comprising at least one, normally a plurality of cycles and
being separated from the following burst by a period of time during
which no ultrasound emission occurs. Thus, it is possible to apply
ultrasound of high intensity during the bursts and nevertheless
keeping the overall intensity of ultrasound at a physiologically
tolerable level.
As ultrasound wave source conventional piezoelectrical transducers
may be used.
While the invention has been decribed in terms of a preferred
embodiment, those skilled in the art will appreciate that various
modifications, substitutions, omissions and changes may be made
without departing from the spirit thereof. Accordingly, it is
intended that the scope of the invention be limited solely by the
scope of the following claims.
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